And something we find in the biomechanical analysis of Cheptegei is that he does not heel strike to create the teeter-totter effect. He basically comes down quite hard on his forefoot and then pushes off. If you notice, he over-pronates quite extensively on his left foot. Remember, one of the big breakthroughs in biomechanical footwear design was engineering propulsion and enabling propulsion of the big toe. I can send you some papers if interested in this.
You seem to misunderstand the teeter totter effect. It doesn’t matter if you land midfoot the transfer of force happens at toe-off. Do me a favour get a fork and a knife out of your cupboard. Put a little square of cheese on the end of the fork handle and then push down on the other end of the fork. What happens to the cheese??? Now try the same with the flat knife. If you are feeling smart try and fashion a fork shaped object out of a foam like a bit of white bread. Where does the cheese go? Nowhere!!!!! Now do you understand what happens at toe-off? The force is transferred to the heel instead of being lost. It requires a stiff curved object like a fork. Welcome to the world of engineering. Now imagine Cheptegei’s heel is the bit of cheese and his forefoot is your finger pushing down on the fork. PROPULSION!!!!!!